Phytoplankton production in the Santa Barbara Channel supports one of the richest marine ecosystems in the Southern California Bight. The climatology of chlorophyll biomass in the area reveals maxima over the Santa Barbara Basin in the western Channel and along the mainland in the eastern channel where the continental shelf broadens and where two rivers discharge seasonally. The patterns and drivers of primary productivity that underpin these chlorophyll distributions were examined on 16 cruises conducted three times per year from 2001 -2006 as part of the Santa Barbara Coastal Long-Term Ecological Research project. Empirical orthogonal function (EOF) analysis revealed three modes of variability that explained 89% of the variance in the productivity data set. The EOF first mode describes productivity within the Santa Barbara Channel that is dominated by coastal upwelling during spring. Upwelling was most intense in the western Channel resulting in productivity maxima over the Santa Barbara Basin during strong equatorward winds. The second EOF mode describes productivity variations over the Santa Barbara Basin and is associated with a cyclonic eddy in the western channel reported in previous studies. High productivity coincided with large values of the second mode during spring and autumn. During spring the eddy entrained plumes of water upwelled along the mainland coast increasing the residence time of developing phytoplankton blooms in the western Channel. In oligotrophic autumn conditions eddy-induced upwelling also increased productivity in the western Channel when vertical nutrient supply was constrained by strong stratification. The third EOF mode describes an along-shore productivity variability in the eastern Channel in which enhanced productivity on the continental shelf occurred during spring and autumn. These events were not related to river discharge or sediment resuspension events as has been hypothesized previously, but their proximity to the mouths of the major rivers discharging into the Channel suggests some indirect relationship to riverine inputs. Overall, our analysis shows that upwelling combined with the effects of cyclonic rotation on particle retention and vertical nutrient supply combine to enhance phytoplankton biomass and productivity in the western Santa Barbara Channel.